Field of the Invention
The invention relates to an apparatus and a method for deforming a jacket tube of a honeycomb body, particularly for cleaning internal combustion engine exhaust gases.
Apparatuses for cleaning exhaust gas are known to have a metal catalyst carrier body. The metal catalyst carrier body is produced by winding or intertwining sheet-metal layers, at least some of which are structured. Such catalyst carrier bodies are described, for example, in European Patent Application 0 245 738, corresponding to U.S. Pat. Nos. 4,803,189 and 4,946,822.
The catalyst carrier bodies are disposed in a jacket tube or housing. The individual sheet-metal layers are joined to one another and to the jacket tube, for instance by brazing, sintering or welding.
The apparatus is integrated into an exhaust system. Since both ends of the apparatus must each be connected to one tube of the exhaust system, the apparatus is connected with a diffusor on the exhaust inlet side and with a reducing piece on the exhaust outlet side. The purpose of the diffusor is to enlarge the flow cross section for the exhaust gas from the cross section of the tube to the cross section of the apparatus, and the purpose of the reducing piece is to reduce the flow cross section on the outlet side of the apparatus to the cross section of the tube which then follows. The joining of the diffusor and of the reducing piece to the apparatus is carried out by welding. That requires that the dimensions of the tube on the inlet and outlet sides of the exhaust gas and the contour of the jacket tube be within certain tolerance limits. Typically, the jacket tube protrudes from 5 to 10 mm beyond both end surfaces of the catalyst carrier body. In order to attain the geometry and dimensions of the jacket tube required for connection to the diffusor and to the reducing piece, the jacket tube is calibrated from the inside before and/or after the insertion of the catalyst carrier body. The calibration has heretofore generally been performed in such a way that a tool which has a plurality of segments is introduced into the jacket tube, and the individual segments are radially spread outward. The spreading of the segments is carried out from the flow limit of the jacket tube material outward, so that in that region the jacket tube is free of stress. Since the segments of the tool are spread radially outward, it is not possible to achieve an exactly predetermined contour.
U.S. Pat. No. 5,096,111 discloses an apparatus for producing a honeycomb body with a jacket tube that includes a plurality of radially displaceable segments, by which the jacket tube of the honeycomb body can be performed. The individual segments are joined by one end to a carrier, which is connected to a piston rod of a cylinder-piston unit. The carrier having the segments is displaceable axially within a cylindrical body and out of it. To that end, the cylinder-piston unit is joined to the cylindrical body. In the inlet region of the cylindrical body, a conical segment is formed, which tapers from the inlet side in the axial direction. In order to deform the jacket tube, a number of segments fit around the jacket tube of the honeycomb body. Next, the honeycomb body is pulled into the cylindrical body through the use of the cylinder-piston unit. The honeycomb body is successively deformed in the conical segment in the course of being pulled in. Once the deformation has been done, the honeycomb body with the segments is pulled out of the cylindrical body by the cylinder-piston unit. During the axial displacement of the segments, the segments slide along the inner jacket surface of the cylindrical body.
Published UK Patent Application GB 2 020 190 A discloses the use of an apparatus that has a plurality of radially movable segments to deform the jacket tube of a honeycomb body. Exhaust gas cleaning apparatuses are also known in which the catalyst carrier body is formed of a ceramic material. Such catalyst carrier bodies are disposed in a two-piece housing. German Utility Model G 87 01 980.9 U1 describes such a housing for receiving a monolithic ceramic body.
Half-shells of the housing are made from one metal sheet by deep drawing. In order to support the ceramic catalyst carrier body, a sheath for the ceramic body is provided between the outside of the carrier body and the housing.
The two housing shells are then pressed together and welded in gas-tight fashion at their contacting surfaces. Corresponding production methods for an apparatus for exhaust gas cleaning with metal catalyst carrier bodies are known from German Patent DE 28 56 030 C2 and European Patent Application 0 117 602 B1, corresponding to U.S. Pat. No. 4,559,205.
The housing parts can be produced with high accuracy. However, it is not possible to produce the ceramic catalyst carrier bodies exactly enough. It is therefore necessary to dimension the housing in such a way that even oversized ceramic catalyst carrier bodies or ceramic catalyst carrier bodies with slight deformations can be integrated into the housing. In order to prevent a gap, through which the exhaust gas flows uncleaned, from forming between the catalyst carrier body and the housing, an intermediate layer is placed there, especially a so-called swelling mat. Other intermediate layers, with wire mesh and the like, are also known. Those layers may also be coated with a catalyst.
It is therefore relatively expensive to produce an apparatus for exhaust gas cleaning that has a ceramic catalyst carrier body.